Lockout valves are known for controlling the flow of fluid, for example pressurized air, in a fluid system. The lockout valves are used in maintenance and service procedures of air-operated equipment in the system. Prior to servicing, a handle or slide on the body of the valve is moved to a closed position, blocking upstream air pressure. At the same time, downstream air pressure is relieved to allow maintenance to the equipment. A padlock can be installed on the valve to deter unauthorized actuation during the maintenance procedure. Following maintenance, the padlock is removed and the handle or slide is moved to an open position, returning air pressure to the system.
One type of lockout valve is offered by the assignee of the present invention under the model/designation "LV" Series Lockout Valve. The lockout valve is typically installed in pneumatic drop legs or individual pneumatic control lines with, for example, a filter, regulator and lubricator. In this type of valve, a handle attached to a cylindrical rod can be grasped and moved between an open and closed position. The cylindrical rod includes circumferential channels which allow air to flow through the valve when it is open, but which are sealed off to prevent air flow through the valve when the valve is closed. A padlock can be inserted through an opening in the valve body and into a groove formed in the handle when the valve is in the closed position. While this lockout valve operates satisfactorily in most conditions, it can be bulky and relatively expensive for certain applications, and contains an arrangement of components which can be time-consuming and complicated to manufacture. Moreover, as the handle is moved from a closed position to an open position, pressurized air enters the system relatively rapidly, which can adversely affect certain equipment in the system, for example cylinders with attached loads.
Patent Specification U.S. Pat. No. 3,780,982 show a gate valve structure having a slab gate with a fully closed position, a second position where small diameter holes provide bleed flow, and a fully opened position, depending upon the rotation of a hand wheel controlling the movement of the valve. While the gate valve structure shown in this reference may be appropriate for certain applications, the valve can be moved to its fully opened position before the pressure is equalized across the valve. Again, equipment in the system can be adversely affected by a rapid increase in pressure.
As such, it is believed that there is a demand in the industry for a lockout valve which is relatively simple in construction and manufacture, and which provides a gradual build-up of pressure across the lockout valve when opened to protect equipment in the system.